Answer 1

See this rudolph flash
https://code.sololearn.com/WRc3A9482I7I/?ref=app

Answer 2

Can you explain this example step-by-step?
const findSum = (arr, sum) =>
arr.some((set => n => set.has(n) || !set.add(sum - n))(new Set));
set is a new Set()
n is arr element
Since some() is used, every element of arr is checked until it is completed or if it gets a True value while executing.
set.has(n) || !set.add(sum - n)
First it checks whether the set has n or not and if it is true, then it will directly return true and stop.
Then, it adds (sum - n) in the set and since ! is added, it will always return False.
Now take this (given in the article)
arr = [3,5,1,4]
sum = 9
1st:
set does not have 3
Add, set = 9-3
set = 6
2nd:
set does not have 5
Add, set = 6, 9-5
set = 6, 4
3rd:
set does not have 1
Add, set = 6, 4, 9-1
set = 6, 4, 8
4th:
set does have 4
Returns True
I am not good at explanations but hope that you will understand it...

Answer 3

https://code.sololearn.com/WgY1uE3EzF0y/?ref=app

Answer 4

rudolph flash Glad I could help. 😄